The World Health Organisation (WHO) has said it is investigating a few dozen cases of two new sub-variants of the Omicron Covid-19 strain.
WHO is taking a closer into both sub-variants to assess whether they are more infectious or dangerous than previous strains.
BA.4 and BA.5 are sister variants of the original BA.1 Omicron variant, a strain which is dominant across the world.
The health body is already tracking BA.1 and BA.2 as well as BA.1.1 and BA.3.
Several dozens of cases of the two new sub-variants have been reported
Danny Lawson
The WHO are investigating BA.4 and BA.5
Denis Balibouse
The WHO said it had begun tracking the new sub-variants because of their "additional mutations that need to be further studied to understand their impact on immune escape potential".
Only a few dozen cases of the two sub-variants had been reported to the global GISAID database so far, the WHO said.
The UK’s Health Security Agency said last week that BA.4 had been discovered in England, Scotland, South Africa, Denmark and Botswana between January 10 to March 30.
Government figures say there has been 281,269 people in the UK who have tested positive for Covid-19 in the last seven days.
A total of 1,613 people have died in the last week, after testing positive for the virus within 28 days of passing away.